Phosphate-Functionalized CeO₂ Nanosheets for Efficient Catalytic Oxidation of Dichloromethane

Abstract

Tuning the nature and profile of acidic and basic sites on the surface of redox-active metal oxide nanostructures is a promising approach to constructing efficient catalysts for the oxidative removal of chlorinated volatile organic compounds (CVOCs). Herein, using dichloromethane (DCM) oxidation as a model reaction, we report that phosphate (PO _x) Brønsted acid sites can be incorporated onto a CeO₂ nanosheet (NS) surface via an organophosphate-mediated route, which can effectively enhance the CeO₂'s catalytic performance by promoting the removal of chlorine poisoning species. From the systematic study of the correlation between PO _x composition, surface structure (acid and basic sites), and catalytic properties, we find that the incorporated Brønsted acid sites can also function to decrease the amount of medium-strong basic sites (O^2-), reducing the formation of chlorinated organic byproduct monochloromethane (MCM) and leading to the desirable product, HCl. At the optimized P/Ce ratio (0.2), the PO _x-CeO₂ NSs can perform a stable DCM conversion of 65-70% for over 10 h at 250 °C and over 95% conversion at 300 °C, superior to both pristine and other phosphate-modified CeO₂ NSs. Our work clearly identifies the critical role of acid and basic sites over functionalized CeO₂ for efficient catalytic CVOCs oxidation, guiding future advanced catalyst design for environmental remediation.